1. Field of the Invention
The instant disclosure relates to a specification establishing method for controlling semiconductor process; in particular, a specification establishing method applied on a non-normal distribution group of semiconductor process.
2. Description of Related Art
Statistical Process Control, or SPC, is a process control tool by mathematical and statistical method. The index of SPC (such as Cp, Cpk or Cpmk) is established with the normal distribution data. SPC is usually used to analyze and evaluate a production process by feedback signals in order to find a system factor, so that the user can take some measures to eliminate the effect of the system factor. Thus, the production process is under control and influenced by a random factor only.
However, for the wafer production plant, when establishing a control mechanism for (wafer), SPC can not be applied on the production process of the new product, because test data of the new product always present a non-normal distribution.
Therefore, one aspect of the instant disclosure is to provide a specification establishing method for controlling semiconductor process that addresses the aforementioned problem.